Hub and bearing assembly

ABSTRACT

A bearing spacer for a wheel assembly which has a hub rotatable about a spindle. The hub has a bearing stop shoulder projecting radially inwardly from an inner circumferential surface of the hub. A bearing is mounted on an outer circumferential surface of the spindle and the bearing spacer is mounted intermediate the stop shoulder and the bearing. The bearing spacer is comprised of an annular member having axially extending inner and outer cylindrical surfaces and radially extending end surfaces. One of the end surfaces extends radially outward from the inner cylindrical surface a radial distance less than the radial extent of the stop shoulder. This end surface is joined to the upper cylindrical surface of the bearing spacer by a surface spaced from the stop shoulder and the inner circumferential surface of the hub. Consequently, the bearing spacer transmits thrust forces from the bearing to the bearing stop shoulder while allowing a large radius on the bearing stop shoulder to reduce undesirable stress concentrations therein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to an improved wheel assembly of thetype which includes a hub rotatable about a spindle, wherein the hubincludes a bearing stop shoulder and, more specifically, a bearingspacer located between the hub and the spindle which is designed toreduce stress concentrations in the bearing stop shoulder area of thehub.

2. Description of the Prior Art

The prior art is best illustrated by U.S. Pat. Nos. 3,726,576 toBarnbrook et al issued Apr. 10, 1973; 3,515,448 to C. W. Williams et alissued June 2, 1970; 3,765,737 to Hatch issued Oct. 16, 1973; 3,156,506to H. B. Scheifele et al issued Nov. 10, 1964 and 4,085,984 to R. W.Cameron issued Apr. 25, 1978. These patents show bearings which haveinner and outer races with a sharp radaii of curvatures in intimatecontact with bearing stop shoulders. It has been found that thesedesigns worked adequately in heavy duty axle assemblies. Morespecifically, these designs are acceptable for hubs and shafts made outof steel.

The present invention is directed to wheel assemblies which have hubsmade of aluminum rather than of steel. The use of aluminum hubs reducesthe weight of the vehicle thus permitting more economical operationthereof. It has been found, however, that using lightweight aluminumhubs in high stress situations has caused cracking of the hub in thearea of the bearing stop shoulder. This stress cracking was not found instronger, heavier steel hubs of similar design. The present invention isdesigned to reduce the stress concentration at the bearing stopshoulders on the aluminum hubs thereby making the use of aluminum hubsin heavy duty vehicles far more reliable.

U.S. Pat. No. 3,156,506 to H. B. Scheifele et al is typical of the priorart applications in which the bearings have sharp radaii on the cornersof their inner and outer races which make close contact with the hubassembly and the shaft assembly. The main concern of the presentinvention is with the hub and, consequently, the outer race of thebearing. In order to use standard bearings, it has been found necessaryto use a bearing spacer to allow a greater radius of curvature on thebearing stop shoulder of the hub. The bearing stop spacer is placedbetween the outer surface of the bearing and the inner surface of thebearing stop shoulder which provides a corner radius much larger thanthat of the standard bearing such as that shown in Scheifele et al.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a wheel assembly includingan aluminum hub which is free from any stress cracking problems.

It is a further object of this invention to provide a bearing spacerwhich reduces stresses in the area of the bearing stop shoulder of thehub.

It is still a further object of this invention to provide a bearing stopspacer which is relatively small in thickness and includes a large innerradius to reduce stresses in the bearing shoulder area of the hub.

It is a still further object of this invention to provide a lightweightwheel assembly which is highly reliable and results in more economicaloperation of the vehicle in which it is installed.

These and other objects of the invention are disclosed in a preferredembodiment of the invention which includes a wheel assembly having a hubrotatable about a spindle. The hub includes a bearing stop shoulderradially inwardly projecting from an inner circumferential surface ofthe hub. A bearing is mounted on an outer circumferential surface of thespindle and a bearing spacer is positioned between the stop shoulder andthe bearing. The bearing spacer is comprised of an annular member havingaxially extending inner and outer cylindrical surfaces and radiallyextending end surfaces. One of the end surfaces extends radially outwardof the inner cylindrical surface a radial distance less than the radialextent of the stop shoulder and is joined to the outer cylindricalsurface by a surface spaced from the stop shoulder and the innercircumferential surface of the hub. This allows the bearing spacer totransmit thrust forces of the bearing to the bearing stop shoulder whileallowing a large radius of the bearing stop shoulder to reduce stresstherein.

These and other objects and advantages of the invention will becomeapparent from the following description of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a wheel assembly including thepresent invention.

FIG. 2 is a perspective of the bearing spacer shown in FIG. 1.

FIG. 3 is a cross-sectional view of the bearing spacer shown in FIG. 2.

DESCRIPTION OF THE INVENTION

With reference to the drawings, there is shown in FIG. 1 a wheelassembly generally indicated as 10. The wheel assembly includes a hub 12and a spindle 14. An inner bearing 16 and an outer bearing 18 arelocated between the spindle and the hub to allow the hub to freelyrotate about the spindle during operation of the vehicle. A bearingspacer 20 is located intermediate the inner bearing 16 and a shoulder 22of hub 12.

The bearing stop shoulder 22 radially inwardly projects from an innercircumferential surface 24 of the hub 12. The bearing 16 is mounted onan outer circumferential surface 26 of the spindle 14 and is positionedbetween the spindle surface 28 and the bearing stop shoulder 22 by thebearing spacer 20. As can best be seen in FIGS. 2 and 3, the bearingspacer 20 is comprised of an annular member having axially extendinginner and outer cylindrical surfaces 30 and 32 respectively. The bearingspacer 20 has radially extending inner and outer end surfaces 34 and 36respectively. End surface 36 extends radially outward from the innercylindrical surface 30 a radial distance less than the radial extent ofthe stop shoulder 22 and is joined to the outer cylindrical surface 32by a surface 38 which in the wheel assembly of FIG. 1 is spaced from thestop shoulder 22 and the inner circumferential surface 24 of the hub 12.

In the preferred embodiment the surface 38 extends axially inwardly atan angle of 45 degrees with respect to the center line of the spindle14. The spacer 20 is designed to permit a relatively large radius 40 andthereby avoid a small corner where the stop shoulder 22 joins thesurface 24 of hub 12. Other angles may be used for surface 38 as long asthe surface 38 clears the large radius 40 of shoulder 22. A step mayalso be used between surface 36 and surface 32 but the angled surface 38is preferred.

As stated above, in the prior art wheel hubs fatigue cracks haveoriginated in the area of the corner where the shoulder 22 joins surface24. The small radius previously provided at the bearing cup shoulder onconventional hubs is required by the standard design of bearings used inthe automotive field which utilize the sharp corners for engagement withthe hub. These sharp corners have been satisfactory when installedadjacent the bearing stop shoulder in hubs made of steel. However, inhubs made of aluminum, cracking, as described above, has occurred.Fatigue cracks are minimized with the use of a bearing spacer asdescribed herein because the bearing spacer allows the rotating hub tohave a generous shoulder radius as shown at 40.

Stress fractures of the type described above occur in automotiveapplications because the hubs rotate on fixed spindles and aresusceptible to fatigue fractures because they experience a complete loadreversal every revolution. The substantial loading on the bearing and,consequently, the bearing stop shoulder are thrust loads which occurduring vehicle operations. Fatigue fractures which resulted from stressconcentrations in the area of the small radius previously used at thebase of the bearing stop shoulder can be minimized by the use of the cupspacer of the present invention. The bearing spacer 20 moves thestandard bearing cup, which has a sharp radius, away from the shoulder22 and the angled surface 38 allows a generous shoulder radius to bemachined in the hub.

The invention described thus provides an improved vehicle wheel assemblyutilizing an aluminum hub which is lighter and far less suseptible tostress failure than those of the prior art.

I claim:
 1. In a land vehicle a wheel assembly including an aluminum hubrotatable about a spindle, said hub including a bearing stop shoulderprojecting radially inwardly from an inner circumferential surface ofsaid hub, a bearing mounted on an outer circumferential surface of saidspindle and a bearing spacer intermediate said stop shoulder and saidbearing, said bearing spacer comprising an annular member having axiallyextending inner and outer cylindrical surfaces and radially extendingend surfaces, one of said end surfaces extending radially outward fromsaid inner cylindrical surface a radial distance less than the radialextent of said stop shoulder and being joined to said outer cylindricalsurface by a surface spaced from said stop shoulder and said innercircumferential surface of said hub whereby said bearing spacertransmits thrust forces on said bearing to said bearing stop shoulderwhile allowing a large radius on the bearing stop shoulder to reduceundesirable stress concentrations therein.
 2. In a land vehicle animproved wheel assembly which includes an aluminum hub rotatable about aspindle, said hub including a bearing stop shoulder projecting radiallyinwardly from an inner circumferential surface of said hub and, abearing mounted on an outer circumferential surface of said spindlewherein the improvement comprises a bearing spacer intermediate saidstop shoulder and said bearing, said bearing spacer having axiallyextending inner and outer cylindrical surfaces and radially extendingend surfaces, one of said end surfaces extending radially outward fromsaid inner cylindrical surface a radial distance less than the radialextent of said stop shoulder and being joined to said outer cylindricalsurface by a surface spaced from said stop shoulder and said innercircumferential surface of said hub whereby said bearing spacertransmits thrust forces on said bearing to said bearing stop shoulder toreduce undesirable stress concentrations therein.
 3. A bearing spacer asset forth in claim 2, wherein said one of said end surfaces is joined tosaid outer cylindrical surface by a surface which is inclined 45 degreeswith the center line of said spindle.